1. Field
This disclosure relates to the bundle adjustment of images.
2. Background
Multiple photographic images of a geographic area may be used to create or update a three-dimensional (3D) representation of the area and of particular structures and other points of interest in that geographic area. For example, oblique imagery of a city area taken from an aircraft may be used to generate a three-dimensional view of city streets, buildings, and other points of interest. In general, multiple images from a set of oblique images overlap an area. In order for these multiple images to be used in generating an accurate representation of the area in 3D, the images are “bundle adjusted.” Bundle adjustment is a technique of determining camera parameters for individual images so that the objects in the images are accurately represented in a corresponding 3D representation. Given a set of images depicting a number of 3D points from different viewpoints and initial parameters regarding the cameras acquiring the images, bundle adjustment can be defined as the problem of simultaneously refining the 3D coordinates describing the scene geometry as well as the parameters of the relative motion and the optical characteristics of the cameras, according to an optimality criterion involving the residual error of corresponding image projections of the 3D points.
The quality of the results of the bundle adjustment process, for example, the accuracy of the determined camera parameters and positions of 3D points and other geographic features, depend upon having sufficient features in images based upon which cameras can be related to each other. In some geographic areas, however, such features may not be present. When two cameras are to be related based upon images of an area that has a lack of detectable features, conventional bundle adjustment techniques may be unable to determine accurate camera parameters and 3D point positions.